条件数据观察点在 ARM GDB 中不起作用
Conditional data watchpoint doesn't work in ARM GDB
我的意图是能够在全局变量具有某个确切值时进行捕获。 GDB 有 data watchpoints 可以根据它来实现。
考虑为 x86 编写的这个简单程序 Linux:
int myVar = 0;
void debug_watchpoints() {
for(int i=0; i < 2000; i++) {
myVar++;
}
}
int main() {
debug_watchpoints();
return 0;
}
用
编译程序
gcc -o main -ggdb3 -Og main.c
并开始使用 GDB 进行调试：
max@PC-LT-23:~/Whosebug$ gdb ./main
GNU gdb (Ubuntu 8.3-0ubuntu1) 8.3
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./main...
(gdb) b main
Breakpoint 1 at 0x1146: file main.c, line 9.
(gdb) start
Temporary breakpoint 2 at 0x1146: file main.c, line 9.
Starting program: /home/max/Whosebug/main
Breakpoint 1, main () at main.c:9
9 int main() {
(gdb) watch myVar if myVar==1337
Hardware watchpoint 3: myVar
(gdb) continue
Continuing.
Hardware watchpoint 3: myVar
Old value = 1336
New value = 1337
debug_watchpoints () at main.c:4
4 for(int i=0; i < 2000; i++) {
(gdb)
如您所见，程序在恰好变量设置为 1337 的时间点停止了程序。
考虑 完全相同的程序，使用 arm-none-eabi-gcc 为具有 Cortex-M4F 内核的 STM32L476RG 微控制器编译。这里使用的 IDE 是 System Workbench for STM32 (aka Eclipse)，工程由 STM32CubeMX 生成。
现在启动 openocd 可获得
Open On-Chip Debugger 0.10.0+dev-00021-g524e8c8 (2019-04-12-08:33)
Licensed under GNU GPL v2
For bug reports, read
http://openocd.org/doc/doxygen/bugs.html
srst_only separate srst_nogate srst_open_drain connect_assert_srst
Info : The selected transport took over low-level target control. The results might differ compared to plain JTAG/SWD
padded zone erase set to 1
adapter speed: 8000 kHz
adapter_nsrst_delay: 100
Info : Listening on port 6666 for tcl connections
Info : Listening on port 4444 for telnet connections
Info : clock speed 8000 kHz
Info : STLINK v2.1 JTAG v34 API v2 M25 VID 0x0483 PID 0x374B
Info : using stlink api v2
Info : Target voltage: 0.011074
Error: target voltage may be too low for reliable debugging
Info : Unable to match requested speed 8000 kHz, using 4000 kHz
Info : Stlink adapter speed set to 4000 kHz
Info : STM32L476RGTx.cpu: hardware has 6 breakpoints, 4 watchpoints
Info : Listening on port 3333 for gdb connections
Info : accepting 'gdb' connection on tcp/3333
target halted due to debug-request, current mode: Thread
xPSR: 0x01000000 pc: 0x08001340 msp: 0x20018000
在main 函数中设置了一个断点，然后观察点的设置与之前完全一样。此外，在执行 debug_watchpoints() 函数后设置断点。
GNU gdb (GNU Tools for Arm Embedded Processors 9-2019-q4-major) 8.3.0.20190709-git
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "--host=x86_64-linux-gnu --target=arm-none-eabi".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word".
(gdb) Reset_Handler () at ../startup/startup_stm32l476xx.s:63
63 ldr sp, =_estack /* Set stack pointer */
Temporary breakpoint 3, main () at ../Src/main.c:65
65 {
(gdb) watch myVar if myVar==1337
Hardware watchpoint 4: myVar
(gdb) info breakpoints
Num Type Disp Enb Address What
2 breakpoint keep y 0x08000f46 in main at ../Src/main.c:70
4 hw watchpoint keep y myVar
stop only if myVar==1337
(gdb)
当继续执行程序时，它现在会在每次用 SIGTRAP 修改变量 时停止 ，无论是否满足条件。
Program received signal SIGTRAP, Trace/breakpoint trap.
0x08000ec2 in debug_watchpoints () at ../Src/main.c:54
54 for(int i=0; i < 2000; i++) {
(gdb) continue
Continuing.
Program received signal SIGTRAP, Trace/breakpoint trap.
0x08000ec2 in debug_watchpoints () at ../Src/main.c:54
54 for(int i=0; i < 2000; i++) {
(gdb) continue
Continuing.
Program received signal SIGTRAP, Trace/breakpoint trap.
0x08000ec2 in debug_watchpoints () at ../Src/main.c:54
54 for(int i=0; i < 2000; i++) {
(gdb) info breakpoint
Num Type Disp Enb Address What
2 breakpoint keep y 0x08000f46 in main at ../Src/main.c:70
4 hw watchpoint keep y myVar
stop only if myVar==1337
(gdb) print myVar
= 3
我可以继续任意多次，每次更改变量时它都会中断。
在我的“调试堆栈上的内存损坏”场景中，我确实需要 GDB 来正确评估条件，否则程序将停止一千次或更多次（每次恰好在此内存中的变量location 被更改了），而不是仅在特定时间将特定值写入其中以捕获错误。
为什么 arm-none-eabi-gdb 的行为与正常的 gdb 不同？难道是Cortex-M4硬件调试能力问题，arm-none-eabi-gdb，或者GDB服务器openocd？
None 我知道的软件开箱即用。当我使用 DWT 时，我通常会在我的软件中设置它。我还没有找到任何方法来通过 gdb 的任何变体对其进行编程（除了手动设置寄存器 - 但它太烦人了）
如前所述，您正在使用的调试器桥接器 openocd 中没有可用的实现。
可以通过sw设置。这是一个小片段。 COMP2、FUNCTION2、COMP1 和 FUNCTION1 是 DWT 寄存器。请注意，您需要使用两个链接在一起的比较器。并非所有 Cortex-m 实现都支持这些功能，并且并非所有比较器都是可链接的，这取决于您的芯片。此外，捕获似乎是异步的。通常我的电脑在触发后会停止一些指令。
DWT->COMP2 = <address to compare>;
DWT->FUNCTION2 = 0;
DWT->COMP1 = <word to compare>;
DWT->FUNCTION1 = 0x20B06;
我的意图是能够在全局变量具有某个确切值时进行捕获。 GDB 有 data watchpoints 可以根据它来实现。
考虑为 x86 编写的这个简单程序 Linux:
int myVar = 0;
void debug_watchpoints() {
for(int i=0; i < 2000; i++) {
myVar++;
}
}
int main() {
debug_watchpoints();
return 0;
}
用
编译程序gcc -o main -ggdb3 -Og main.c
并开始使用 GDB 进行调试：
max@PC-LT-23:~/Whosebug$ gdb ./main
GNU gdb (Ubuntu 8.3-0ubuntu1) 8.3
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./main...
(gdb) b main
Breakpoint 1 at 0x1146: file main.c, line 9.
(gdb) start
Temporary breakpoint 2 at 0x1146: file main.c, line 9.
Starting program: /home/max/Whosebug/main
Breakpoint 1, main () at main.c:9
9 int main() {
(gdb) watch myVar if myVar==1337
Hardware watchpoint 3: myVar
(gdb) continue
Continuing.
Hardware watchpoint 3: myVar
Old value = 1336
New value = 1337
debug_watchpoints () at main.c:4
4 for(int i=0; i < 2000; i++) {
(gdb)
如您所见，程序在恰好变量设置为 1337 的时间点停止了程序。
考虑 完全相同的程序，使用 arm-none-eabi-gcc 为具有 Cortex-M4F 内核的 STM32L476RG 微控制器编译。这里使用的 IDE 是 System Workbench for STM32 (aka Eclipse)，工程由 STM32CubeMX 生成。
现在启动 openocd 可获得
Open On-Chip Debugger 0.10.0+dev-00021-g524e8c8 (2019-04-12-08:33)
Licensed under GNU GPL v2
For bug reports, read
http://openocd.org/doc/doxygen/bugs.html
srst_only separate srst_nogate srst_open_drain connect_assert_srst
Info : The selected transport took over low-level target control. The results might differ compared to plain JTAG/SWD
padded zone erase set to 1
adapter speed: 8000 kHz
adapter_nsrst_delay: 100
Info : Listening on port 6666 for tcl connections
Info : Listening on port 4444 for telnet connections
Info : clock speed 8000 kHz
Info : STLINK v2.1 JTAG v34 API v2 M25 VID 0x0483 PID 0x374B
Info : using stlink api v2
Info : Target voltage: 0.011074
Error: target voltage may be too low for reliable debugging
Info : Unable to match requested speed 8000 kHz, using 4000 kHz
Info : Stlink adapter speed set to 4000 kHz
Info : STM32L476RGTx.cpu: hardware has 6 breakpoints, 4 watchpoints
Info : Listening on port 3333 for gdb connections
Info : accepting 'gdb' connection on tcp/3333
target halted due to debug-request, current mode: Thread
xPSR: 0x01000000 pc: 0x08001340 msp: 0x20018000
在main 函数中设置了一个断点，然后观察点的设置与之前完全一样。此外，在执行 debug_watchpoints() 函数后设置断点。
GNU gdb (GNU Tools for Arm Embedded Processors 9-2019-q4-major) 8.3.0.20190709-git
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "--host=x86_64-linux-gnu --target=arm-none-eabi".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word".
(gdb) Reset_Handler () at ../startup/startup_stm32l476xx.s:63
63 ldr sp, =_estack /* Set stack pointer */
Temporary breakpoint 3, main () at ../Src/main.c:65
65 {
(gdb) watch myVar if myVar==1337
Hardware watchpoint 4: myVar
(gdb) info breakpoints
Num Type Disp Enb Address What
2 breakpoint keep y 0x08000f46 in main at ../Src/main.c:70
4 hw watchpoint keep y myVar
stop only if myVar==1337
(gdb)
当继续执行程序时，它现在会在每次用 SIGTRAP 修改变量 时停止 ，无论是否满足条件。
Program received signal SIGTRAP, Trace/breakpoint trap.
0x08000ec2 in debug_watchpoints () at ../Src/main.c:54
54 for(int i=0; i < 2000; i++) {
(gdb) continue
Continuing.
Program received signal SIGTRAP, Trace/breakpoint trap.
0x08000ec2 in debug_watchpoints () at ../Src/main.c:54
54 for(int i=0; i < 2000; i++) {
(gdb) continue
Continuing.
Program received signal SIGTRAP, Trace/breakpoint trap.
0x08000ec2 in debug_watchpoints () at ../Src/main.c:54
54 for(int i=0; i < 2000; i++) {
(gdb) info breakpoint
Num Type Disp Enb Address What
2 breakpoint keep y 0x08000f46 in main at ../Src/main.c:70
4 hw watchpoint keep y myVar
stop only if myVar==1337
(gdb) print myVar
= 3
我可以继续任意多次，每次更改变量时它都会中断。
在我的“调试堆栈上的内存损坏”场景中，我确实需要 GDB 来正确评估条件，否则程序将停止一千次或更多次（每次恰好在此内存中的变量location 被更改了），而不是仅在特定时间将特定值写入其中以捕获错误。
为什么 arm-none-eabi-gdb 的行为与正常的 gdb 不同？难道是Cortex-M4硬件调试能力问题，arm-none-eabi-gdb，或者GDB服务器openocd？
None 我知道的软件开箱即用。当我使用 DWT 时，我通常会在我的软件中设置它。我还没有找到任何方法来通过 gdb 的任何变体对其进行编程（除了手动设置寄存器 - 但它太烦人了）
如前所述，您正在使用的调试器桥接器 openocd 中没有可用的实现。
可以通过sw设置。这是一个小片段。 COMP2、FUNCTION2、COMP1 和 FUNCTION1 是 DWT 寄存器。请注意，您需要使用两个链接在一起的比较器。并非所有 Cortex-m 实现都支持这些功能，并且并非所有比较器都是可链接的，这取决于您的芯片。此外，捕获似乎是异步的。通常我的电脑在触发后会停止一些指令。
DWT->COMP2 = <address to compare>;
DWT->FUNCTION2 = 0;
DWT->COMP1 = <word to compare>;
DWT->FUNCTION1 = 0x20B06;